
#include <stdio.h>
int main()
{
	long x = 1;
	long sum = 0;
	long flag = 1;
	long i = 0;
	for (x = 1; x <= 101; x=x+2)
	{
		i = x * flag;
		sum += i;
		flag *= -1;
	}
	printf("sum=%ld", sum);
	return 0;
}